"300 ppi" means absolutely nothing by itself. The important thing is how many pixels.
You can have a file of 2 x 2 pixels at 300 ppi. That doesn't mean it's high resolution, it just means it will print microscopically small. Pixels per inch. It means exactly what it says.
When you reduce pixels, it becomes pixelated, by definition.
Are you zooming in beyond 100%? If you do, you will see pixels.
900 x 675 is around traditional website size. It should display at 100% at a fairly comfortable size on most screens. But don't zoom in.
When I resize it the pixes reduce from 3600 x 2700 to 900 x 675.
Two questions can help us figure this out:
This is important because no matter how many pixels are in the Smart Object, the number of pixels that can be displayed from it may be limited by the pixel dimensions of the containing Photoshop document, and whether it uses just a portion of the pixels (scaled down) in the containing document.
For example, if you have a 1000 x 1000 pixel JPEG file, and you add it as a Smart Object to a 500 x 500 pixel Photoshop document and make it fit within the edges, the 1000 x 1000 pixel JPEG must appear as a 500 x 500 pixel layer. And then, if you reduced the Smart Object to be 200 x 200 pixels, then the 1000 x 1000 pixel JPEG appears as a 200 x 200 pixel layer.
If your goal is to see all of the pixels of the JPEG Smart Object when zooming in, regardless of how far down it’s scaled, you will need to either increase the pixel dimensions of the Photoshop document, or switch to a vector-based application such as Adobe InDesign or Adobe Illustrator. But also understanding that whether the final published image shows all that detail depends on the resolution of the final display (96 ppi screen, 2400 ppi print, etc.) and how large the image is shown on it.
@Conrad C This is just the classic misunderstanding of resolution. The OP is wondering why they lose resolution when creating a low-res image. For some reason, people believe that you can transform an image without losing detail.
you don't retain those pixels. You're scaling from 9,720,000 pixels to 607,500 pixels and all those pixels are thrown away when you scale.
Sounds like the same issue; too few pixels and the idea that 300dpi has a meaning in terms of image quality; it doesn't.
Thank you all for your input. I appreciate it.